Human judgment isn’t just influenced by bias—it’s riddled with noise, a concept that authors By Daniel Kahneman, Olivier Sibony & Cass R. Sunstein **define as unwanted variability in judgments that that would be expected to be identical.
If two people, or even the same person at two different times, look at the same case, evidence, or problem and reach different conclusions for reasons that should be irrelevant, that’s noise.
Kahneman, Nobel Prize–winning psychologist and author of Thinking, Fast and Slow,* teamed up with business scholar Sibony and legal expert Sunstein to reveal how widespread the phenomenon of “noise” is.
While bias pulls judgments in a consistent direction, noise creates scatter: Unpredictable, invisible inconsistencies that organizations rarely measure and frequently overlook.
The authors argue that this hidden randomness quietly shapes decisions in courtrooms, hospitals, financial institutions, HR departments, and beyond—often causing more harm than bias itself.
By exposing how these inconsistencies arise and how they can be systematically reduced, Noise challenges the notion that experts naturally converge on the same answer.
1. System noise is louder than noticed
One of the most striking findings in the book comes from “noise audits,” where organizations test how much their experts disagree with one another.
Across industries, from underwriting to recruitment to forensic science, Kahneman and co-authors found that leaders chronically underestimate how inconsistent their professionals are. This creates system noise.
For example, a typical executive team might predict that their managers’ judgments differ by about 10%. In reality, noise audits reveal variability closer to 40%–60%.
This means organizations often operate under illusions of consistency that don’t exist in the way it is assumed.
The insight isn’t just “people disagree.” It’s that organizations are blind to how massive this disagreement is, and this blind spot quietly erodes fairness, accuracy, and profit.
2. The types of noise
The authors distinguish between different types of noise:
- Level Noise: Judges or decision-makers have consistently higher or lower “baselines.”
- Pattern Noise: Judges behave inconsistently across similar cases. Different decisions are made based on context, mood, order of information, or irrelevant details.
Some level noise is to be expected. However, the real shock is how much pattern noise exists and how little organizations do to address it.
The book shows that professionals often believe experience eliminates variability. In fact, experience frequently increases pattern noise because people develop idiosyncratic judgment habits.
This challenges a reassuring corporate myth that expertise leads to uniformity. Noise demonstrates that expertise without structured decision processes simply creates more individualized inconsistency.
3. Mood, weather & timing alter judgments
One of the book’s most unsettling contributions is the body of research showing that completely irrelevant factors—invisible to both the decision-maker and the people affected—shift outcomes.
The authors highlight empirical data demonstrating that judges tend to give harsher rulings before lunch and doctors interpret identical X-rays differently depending on workload.
The implication is profound. Noise is not just professional disagreement but also unintentional emotional and situational drift.
As much as we want to pretend that our personal lives are separate from our professional selves, they never are.
We are whole beings who are meaningfully impacted by our surroundings. The context of our lives and our emotional well-being overlap with our work.
This reinforces the book’s central point that inconsistency isn’t a flaw of a few bad decision-makers. It is a universal human characteristic.
4. Decision hygiene vs bias training
The authors introduce a concept called decision hygiene. It is the systematic procedures that reduce noise by minimizing opportunities for random variation.
Unlike bias training, which often has weak long-term results, decision hygiene is fundamentally structural.
Examples include:
- Structuring complex judgments into smaller, independent assessments
- Using guidelines or scoring systems before integrating intuitive responses
- Having multiple independent assessors whose views are aggregated rather than discussed to avoid “group contamination”.
These practices are not about eliminating subjectivity. They’re about preventing subjective judgments from drifting unpredictably.
Decision hygiene does not promise perfection but it promises consistency. According to the authors, consistency alone dramatically improves decision quality.
5. The role of intuition
Unlike many conservative approaches to organizational decision-making, Noise does not dismiss intuition. Instead, it proposes that intuition is best employed in environments that provide reliable, rapid feedback and where patterns are proven stable over time.
See the following examples:
- Chess masters develop valid intuitions because the “rules of the world” are consistent and feedback is immediate.
- Hiring managers do not—because human performance is unpredictable and feedback loops stretch months or years.
In the context of Noise, the issue is not whether intuition is good or bad, but whether the environment is one where intuition can realistically be calibrated.
This takeaway matters because noise often masquerades as intuition, and unchecked intuition brings enormous variability.
The authors advocate for “disciplined intuition”. This is a model in which intuitive judgments are allowed but only after structured, noise-reducing steps are completed.
Collaborative critical thinking
Noise is a powerful read for anyone working in decision-heavy fields. Business leaders, policy makers, HR professionals, judges, doctors, journalists, and educators can all greatly benefit from the insights.
It can also help develop decision-making in personal matters.
Noise helps expose how inconsistency distorts human judgment while offering practical ways to reduce it.
With this framework, Kahneman, Sibony, and Sunstein inspire us to be critical and curious about professional reliability — reinforcing the value in collaboration, teamwork and diversity.
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